Method and apparatus for reducing noise generated by the accumulation of carriers in a conveyor system

ABSTRACT

An apparatus and method for reducing the noise generated by colliding conveyor carriers is disclosed which comprises urethane bumpers and a method of attaching same to portions of the carriers that do not make contact with other carriers when the carriers are accumulated. The bumpers extend from the carriers a sufficient distance to contact a similar bumper on an adjacent carrier when one carrier rolls up against another. The bumpers do not prevent the normally contacting portions of the carriers from coming into contact, but merely absorb a portion of the kinetic energy of the moving carrier to reduce the noise generated when the contacting portions of the trolleys do meet, and the presence of these bumpers does not adversely affect the spacing of the carriers in the accumulation line.

The present invention is directed to a method and apparatus for reducingthe noise caused by carriers impacting against one another in theaccumulation portion of a conveyor line, and more specifically to amethod and apparatus for reducing the noise caused by carrier impactswithout significantly altering the spacing between the carriers in theaccumulation line.

BACKGROUND OF THE INVENTION

Power and free conveyors are well known systems made up of a power trackand a free track and a pair of trolleys capable of traveling along thefree track and supporting a carrier. Each leading trolley in a power andfree system includes a driving dog portion which extends toward thepower track and which is engageable by a pusher dog carried by a movingchain on the power track. When the pusher dog and the driving dog areengaged, the trolley is pushed along the free track by the moving powerchain. When the driving dog is retracted, or otherwise disengaged fromthe pusher dog, the trolley stops moving.

Power and free conveyors often include accumulation tracks or sectionswhere a number of carriers can be stored in a closely spaced orcontacting relationship out of the way of the main portion of theconveyor system until they are needed. In order to accumulate carriers,it is necessary to disengage the driving dogs of the trolleys supportingthe carriers from the pusher dog. This is usually accomplished by havingthe accumulation section of the track at a different elevation than themain portion of the track so that a carrier directed into theaccumulation portion will roll down and away from the pusher until itruns into a stationary object The slope must be steep enough to ensurethat the carrier moves quickly away from the pusher to avoid jams and toimpart a sufficiently high speed to the carrier to ensure that itcontinues to roll along the accumulation section of track until itcontacts a stop or another carrier. Additional carriers can beaccumulated in this manner until the accumulation section of track isfull. However, because carriers are periodically removed from thedownstream end of the accumulation section, new carriers can becontinuously accumulated.

Trolleys and carriers are made of steel or similar alloys andconsequently are quite heavy. Each pair of trolleys supports a carrierwhich is also very massive and which may be supporting a heavy workpieceat any given time. Such carriers possess large kinetic energies whenthey roll along the accumulation section of the conveyor track, and thisenergy must be dissipated in order to stop the carrier. Because thecarriers and trolleys are made from metal, a significant amount ofenergy from each collision between carriers is dissipated as soundwaves, and each impact produces a relatively loud noise. Since a givenconveyor line may have multiple accumulation portions, and a plant mayhave multiple conveyor lines each equipped with multiple accumulators,the noise produced by the accumulation of carriers is substantial andfrequent. This noise can be unpleasant to anyone in a plant whereaccumulators are used, and, to employees required to work in closeproximity to these accumulators, the noise can have adverse healthaffects as well.

The high frequencies generated by this metal-to-metal contact can beparticularly damaging to hearing. In addition, the trolleys are oftennot accumulated at regular intervals. Thus, the sound of each successiveimpact may come as something of a surprise to nearby employees. Anemployee who is startled by such sudden noises may have difficultyconcentrating on his job. Attempts have been made, therefore, to reducethe noise created by these accumulations. The normal solution is to coatthe metal surfaces normally making contact with rubber or a similarmaterial which will absorb the impact of the collisions. While this canreduce the noise problem to some extent, it also increases the spacingbetween adjacent carriers in an accumulation line, especially whenenough cushioning material is used to reduce the noise level by anoticeable amount. This increased spacing changes the location of eachtrolley in the accumulation line and makes it difficult for a systemcontroller to keep track of the carriers. In addition, this alteredspacing may prevent the carriers from aligning properly with otherelements of the conveyor system, such as unloading platforms along theaccumulation track. In addition, adding these materials to existingsystems usually requires that the trolleys be modified to accommodatethe cushioning. This is often cost prohibitive. It would therefore bedesirable to reduce the noise generated by the accumulation of carriersin a conveyor line without adversely affecting the spacing of thecarriers, and which noise reduction could be employed on existingsystems without extensively modifying the carriers.

SUMMARY OF THE INVENTION

These and other problems are addressed by the present invention whichcomprises an improved conveyor carrier having a number of resilientbumpers attached to portions of the carriers that do not make contactwith other carriers when the carriers are accumulated. The bumpers areconfigured so that they make contact with one another before the metalcontact surfaces of the carriers collide. The bumpers can be madesufficiently large to absorb a large portion of the force of impactbetween carriers, yet their positioning away from the normallycontacting surfaces prevents them from adding significantly to thespacing between carriers in an accumulation line. In addition, thebumpers are preferably made from a somewhat resilient material so thatthe sound generated by their impact is quieter and at a lower frequencythan the sound generated by a metal-to-metal impact. It has been foundthat the noise caused by the accumulation of carriers can be reduced toan acceptable level in this manner and that it is not necessary toeliminate metal-to-metal contact completely.

In a preferred embodiment, the bumpers are made from urethane and can beretrofitted to existing carriers by bolting them to the openings on thetrolleys normally used to connect the support platform of the carrier tothe trolleys. The bumpers include an attachment portion which fitsbetween two spaced-apart walls on existing trolleys. A bore is providedin the attachment portion which is aligned with existing bores in thetrolley, and a bolt is passed through these aligned openings to hold thebumper in place. The bumpers also include a main body portion, much ofwhich is disposed above or below the trolley body. The bumpers are sizedso that they make contact before any other portions of the trolleys makecontact and absorb a portion of the energy of impact. By attaching thesebumpers to portions of the trolleys that do not normally make contact,significant noise reduction can be achieved without adversely affectingthe intertrolley spacing.

It is therefore a primary object of the present invention to provide amethod and apparatus for reducing the noise produced when two objectscollide.

It is another object of the present invention to provide a method andapparatus for reducing the noise produced by the accumulation ofcarriers in a conveyor line.

It is a further object of the present invention to provide a bumper forabsorbing some of the force of a moving carrier as it impacts againstanother object.

It is yet another object of the present invention to reduce the noisegenerated by colliding carriers while not significantly changing thespacing between the carriers.

It is yet a further object of the present invention to provide a methodfor reducing the amount of high frequency noise generated by thecollision of two metal objects.

It is still another object of the present invention to provide a methodfor mounting bumpers on conveyor carriers which reduces the noisegenerated by the accumulation of the carriers without significantlyincreasing the spacing between the carriers in an accumulation line.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the present invention will become apparentfrom a reading and understanding of the following detailed descriptionof a preferred embodiment together with the following drawings of which:

FIG. 1 is a pictorial view of a trolley bumper according to the presentinvention;

FIG. 2 is a side elevational view of a number of carriers in anaccumulation line equipped with the bumpers shown in FIG. 1; and,

FIG. 3 is a side elevational detail view, partly in section, of two ofthe trolleys shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein the showings are for the purposeof illustrating a preferred embodiment of the present invention only andnot for the purpose of limiting same, FIG. 1 shows a bumper 10 having amain body portion 12 with a width W1 and an attachment portion 14 with awidth W2 formed from a single piece of material, preferably urethane.Main body portion 12 includes an outwardly bowed front contacting wall16, parallel side walls 18, parallel top and bottom walls 20 and a rearwall 22 normal to side walls 18 and angled with respect to front wall16. The angle of rear wall 22 with respect to the side walls gives eachof the side walls 18 a trapezoidal shape. Attachment portion 14 projectsfrom the central portion of rear wall 22 and includes a top wall 24 anda parallel bottom wall 26 which walls extend continuously from top andbottom walls 20 of main body portion 12. Top wall 24 includes a blindbore 28 located above and extending toward rear wall 22 of main bodyportion 12. Attachment portion 14 further includes parallel side walls30 perpendicular to top wall 24 and a bore 32 extending through portion14 between these side walls. Width W2 of attachment portion 14 is lessthan width W1 of main body portion 12 and therefore sections of mainbody portion rear wall 22 are exposed on either side of attachmentportion 14.

FIG. 2 shows a number of carriers 34 comprising support platforms 36,trailing trolleys 42 and leading trolleys 40. The trolleys are equippedwith bumpers 10 and are supported for rolling movement on a track 44.The leading and trailing trolleys have many identical parts and the samereference numerals will be used to identify parts common to bothcarriers. As best seen in FIG. 3, the trolleys each comprise a body 46to which support wheel axles 48 are attached for holding support wheels50 and to which guide wheel axles 52 are attached for holding guidewheels 54. Each trolley 40, 42 further includes parallel spaced apartflanges 56 depending from the undersides of the trolleys for supportingplatforms 36. Flanges 56 of each trolley are spaced apart by a gap 57and each flange 56 includes several openings 58 aligned with similaropenings in the opposite flange 56 for receiving a bolt 59 to attach thesupport platforms to the trolley. Flanges 56 include front and rear ends60 which do not come into contact with other trolleys when the trolleysare accumulated in a line.

Trailing trolley 42 includes a wing 62 extending rearwardly from the topportion of body 46, and leading trolley 40 includes a contact wall 64 atthe top portion of body 46. Wing 62 and contact wall 64 are thecontacting portions of the trolleys, and it is these portions of thetrolleys that normally make contact when the carriers are accumulated.The trolley bodies 46, including wing 62 and contact wall 64, are madeof metal and thus a load noise is generated when these portions of thetrolleys collide.

A bumper 10 is attached to the rear portion of each trailing trolley andthe forward portion of each leading trolley by inserting attachmentportion 14 into gap 57 flanges 56 so that the bore 32 on the bumper isaligned with one of the openings 58 in flanges 56. A bolt 66 is thenpassed through these aligned openings and secured to flange 56 with anut 68. The bumper is held in place by the tight fit between the spacedapart flanges as well as by the compressive force of the nut and boltcombination. Guide wheel axle 52 which extends downwardly into gap 57 isaccommodated by blind bore 28 in top wall 24 of the bumper. Rear wall 22of the bumper is angled at an angle supplementary to the angle of ends60 so that bottom walls 20 and 26 of the bumper are aligned with thebottom portion of walls 56 and so that front wall 16 of the bumper isgenerally perpendicular to track 44. The distance between rear wall 22and front wall 16 of the bumper is chosen such that when the bumpers oftwo adjacent trolleys are at rest and in contact with one another, wing62 and contact wall 64 are separated by a distance of about one halfinch, more preferably by about one quarter inch, and ideally by aboutone eighth of an inch.

This spacing is not sufficient to prevent contact between wing 62 andwall 64 when a carrier is accumulated. Instead, when one carrier makescontact with another, wall 16 of bumper 10 on the moving trolley comesinto contact with wall 16 of bumper 10 on the stationary trolley and thebumpers are compressed by the force of the moving carrier until wall 64collides with wing 62 to stop the carrier. The impact of the urethanebumpers against one another generates less noise than the impact ofmetal against metal because much of the energy of impact is absorbed bythe deformation of the urethane bodies instead of being converted intosound waves. The sound produced is also at a lower frequency and thus isnot as penetrating as the sound of metal on metal. The compression ofthe bumpers absorbs a sufficient amount of energy so that when wing 62and wall 64 finally meet, wall 64 is traveling at a lower speed than itwould have been absent the bumpers and consequently the impact producesa much softer sound. After impact, the urethane bumpers return to theiroriginal shapes which separates wing 62 from wall 64. The spacingbetween the wing and the wall, however, is quite small, preferably onthe order of one eighth of an inch. The eighth carrier in anaccumulation line where these bumpers are used, for example, will onlybe out of place by one inch as compared to the eighth carrier in a lineof carriers which do not include bumpers. This small spacing does notadversely affect the monitoring of the carriers or the control of thesystem.

The present invention has been described in terms of a preferredembodiment, it being understood that numerous modifications of thesubject bumper and carrier will become apparent to those skilled in theart upon a reading and understanding of the foregoing description. Forexample, the shape of the bumper could easily be altered to allow it tobe attached to a trolley of a different design and the bumpers could beattached at other locations on the trolleys or even on the carrierswithout exceeding the scope of this invention. It is intended that allsuch changes and modifications be included in this invention to theextent that they are described by the several claims appended hereto.

We claim:
 1. A conveyor system comprising a support track, a firstcarrier supported on said support track by a leading trolley and atrailing trolley, a second carrier supported on said support trackdownstream from said first carrier by a leading trolley and a trailingtrolley, wherein each of said leading trolleys including a frontcontacting planar stop surface, and each of said trailing trolleysincluding a rear contacting planar stop surface, said front contactingplanar stop surface of a second carrier leading trolley facing the rearcontacting planar stop surface of a first carrier trailing trolley,afront bumper connected to said second carrier leading trolley and havinga front contacting face; and, a rear bumper connected to said firstcarrier trailing trolley and having a rear contacting face; wherein theplanar stops surfaces are spaced apart a distance when the front andrear contacting faces initial contact each other.
 2. The conveyor systemof claim 1 wherein the distance between the front and rear stop surfacesis about one half inch.
 3. The conveyor system of claim 1 wherein thedistance between the front and rear stop surfaces is about one quarterinch.
 4. The conveyor system of claim 1 wherein the distance between thefront and rear stop surfaces is about one eighth inch.
 5. The conveyorof claim 1 wherein each of said bumpers are resilient.
 6. The conveyorof claim 5 wherein each of said bumpers are comprised of urethane. 7.The conveyor of claim 6 wherein each of said bumpers includes a firstface conforming to a surface of said trolley.
 8. The conveyor of claim 1wherein said bumpers are compressible to allow contact between saidsecond carrier leading trolley contacting surface and said first carriertrailing trolley contacting surface when said second carrier collideswith said first carrier.
 9. The conveyor of claim 1 wherein said frontbumper comprises:a main body portion having a top wall, a bottom wallspaced apart from and parallel to said top wall, first and secondparallel side walls extending between said top wall and said bottomwall, a front wall connected between said side walls and said top andbottom walls, and a rear wall normal to said side walls and angled withrespect to said front wall; and an attachment portion having (i)parallel top and bottom walls contiguous with said main body portion topwall and bottom wall, (ii) parallel spaced apart side walls extendingfrom the main body portion rear wall and between said attachment portiontop and bottom walls, and spaced inwardly of the first and secondparallel side walls of the main body portion, and (iii) a bore extendingthrough said attachment portion between said parallel and spaced apartside walls, an axis of said bore generally parallel to the rear wall ofthe main body portion.
 10. The conveyor of claim 9 wherein said frontand rear bumpers are comprised of urethane.
 11. A method for reducingnoise generated in a conveyor system by the accumulation of carriershaving planar-contacting surfaces while maintaining a close spacingbetween the contacting surfaces of the carriers, the planar contactingsurfaces of adjacent carriers facing each other, the method comprisingthe steps of:a) mounting bumpers on surfaces of said carriers; b)propelling one carrier into a downstream carrier; c) reducing noisegenerated when the bumper of the one carrier strikes the bumper of thedownstream carrier before the facing planar-contacting surfaces collide;and d) accumulating the one carrier with the downstream carrier with aspace between the facing planar-contacting surfaces.
 12. The method ofclaim 11 wherein the step of mounting bumpers comprises the steps ofinserting a portion of said bumper into a space on an existing trolleyand passing a bolt through an existing opening in said trolley and anopening in said portion.
 13. A conveyor system comprising a supporttrack, and a first trolley and a second trolley supported on saidsupport track for movement therealong, wherein said trolleys eachinclude at least one metallic contacting surface and at least oneresilient contacting surface, the resilient contacting surfacesextending from a portion of each trolley such that said metalliccontacting surfaces of said first and second trolleys contact oneanother only after said resilient contacting surface of said secondtrolley has contacted said resilient contacting surface of the firsttrolley, the metallic contacting surfaces being spaced from each otherafter contact and when the trolleys are at rest as a result of thesizing of the resilient contact surfaces of each trolley.
 14. Theconveyor system of claim 13 comprising a bumper mounted on each trolley,each bumper having the resilient contacting surface.
 15. The conveyor ofclaim 14 wherein each bumper extends from each respective trolley adistance to ensure that contact between the resilient contactingsurfaces of the respective trolleys occurs prior to contact between themetallic contacting surfaces of the respective trolleys.
 16. Theconveyor system of claim 1 comprising:an accumulation track connected tosaid support track for accumulating a plurality of carriers in a closelyspaced relationship; and a pusher for selectively pushing said carriersonto said accumulation track.
 17. The conveyor system of claim 16wherein said carriers include platform portions.